The present invention relates generally to vent valves and vent valves specifically designed for use in electropneumatic brake control valves.
Electropneumatic brake control valves are well known in the passenger railroad art and the mass transit railroad art. Because the trains are short and are not involved generally in a mix and match at an interchange of different equipment, the ability to provide pneumatic and electrical control throughout the train has been readily available in the passenger and the mass transit systems. In freight trains, the trains may involve as much as 100 cars stretching over one mile or more. The individual cars may lay idle in harsh environments for up to a year without use. Also, because of the long distance they travel, the cars are continuously moved from one consist to another as it travels to its destination. Thus, the use of electropneumatic-pneumatic valves in the freight trains has been very limited.
Recently, electropneumatic brake control valves have been introduced for freight trains. A typical example is the EP-60.RTM. available from New York Air Brake Corporation and illustrated in U.S. Pat. No. 5,967,620 to Truglio et al.
An overlay system of the prior art is illustrated in FIG. 1 herein which shows a car control device 40 connected between the emergency portion 20 and the pipe bracket 30. A service portion 10 is also connected to the pipe bracket 30. The connection of the car control device 40 to the pipe bracket 30 at the service interface and a vent valve 54 on the emergency interface of the prior art is illustrated in FIG. 2 herein. The vent valve 54 is a KM-2 available from New York Air Brake Corporation and Knorr-Bremse AG. The car control device 40 on the service interface of pipe bracket 30 has been used with a full emergency section portion 20 on the emergency interface as illustrated in FIG. 3. FIGS. 2 and 3 are considered stand alone and not overlay systems as in FIG. 1 in that the car control device 40 performs an electropneumatic operation of the vehicle brakes with a pneumatic emergency application if the car control device 40 fails. The purpose of the vent valve 54 and the emergency portion 20 in the stand alone is to vent the brake pipe in an emergency situation thereby propagating the emergency condition in the brake pipe. This will also cause the pneumatic portion of the car control device 40 to apply the car brakes.
The KM-2 vent valve has a slower transmission rate than the standard emergency portion 20 of a pneumatic valve. To compensate for this, the emergency brake cylinder build up rates were increased to maintain the stop distance required. This resulted in increase in-train forces which are undesirable.
The use of a standard pneumatic emergency portion 20, illustrated in FIG. 3 in the stand alone as a vent valve, also has its drawbacks. The accelerated application portion of the emergency portion 20 when used with the CCD 40 causes an operational problem in which the valve will waste air by venting in response to minor fluctuations in brake pipe during normal EP brake operations. It should be noted that during EP brake operation, the brake pipe should be fully charged. Minor variations do occur. The brake pipe fluctuation comes about on release and recharge of the brake pipe which in turn replaces reservoir air used during the previous brake application. This is monitored by the valves in the emergency portion 20 which causes undesired venting of brake pipe, by the elements in the emergency brake portion 20 thus wasting air and slowing the recharge process.
Also, the inshot portion of the emergency brake valve portion 20 provides a two-stage build up of brake cylinder pressure. Although being required in a totally pneumatic system, it limits the use of the electropneumatic brake control valve to a single car set because of the pneumatic capacity. It would take too long to build up the pressure in both car sets.
The present invention is a vent valve to be used with a brake control valve having a pipe bracket with an emergency portion interface. The vent valve includes an emergency portion body with an interface configured to mate with the emergency portion interface of the pipe bracket. The body includes the vent valve for selectively connecting a first brake pipe port to a vent port in the body and a vent piston controlling the vent valve. The vent piston has a first side connected to a volume port in the pipe bracket. The body also includes a discharge valve selectively connecting the second side of the vent piston to either the vent port or a volume port at the interface. An emergency piston controls the discharge valve and includes a first side connected to the volume port and the second side connected to a second brake pipe port at the interface. These are standard elements of the emergency portion. The body does not include at least one of the inshot valve and an acceleration application valve. The removal of the inshot valve allows acceptable application of the multiple brake set and the absence of the acceleration application valve prevents undesirable air loss.
The body includes a casting with at least one cover. The casting includes all cavities and passages of a standard emergency portion. The cover for the vent valve and inshot cavity includes only the passage connecting the first side of the vent valve to the volume port. The cavities for the accelerated application valve and the an emergency auxiliary release valve in the casting remain plugged. The body also does not include a high pressure valve which was included as part of the original vent valve/inshot valve cover. The body does include an accelerated application sensor valve operated by the emergency piston and does not include an accelerated application valve. The discharge valve and the accelerated application sensor valve are poppet valves in line with the emergency piston.
The vent valve formed from a standard emergency portion is used in an electropneumatic brake for a railroad vehicle. It is attached to the pipe bracket at the emergency interface of a pipe bracket. An electropneumatic car brake control device is mounted on the service interface of the pipe bracket. The pipe bracket includes the volume connected to the volume port at the emergency interface.
A method of converting a standard emergency brake valve portion includes removing at least one of the inshot valve and the accelerated application valve and then plugging the corresponding cavity. It also includes removing an emergency accelerated release valve and plugging its cavity. It may also include removing the high pressure valve and plugging its cavity.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.